Conventionally, video, audio and other functional chips are independently designed for corresponding applications. Nowadays, it has become a trend to integrate circuitry of different functions in a single IC chip so as to enhance performance and reduce cost. For example, a liquid crystal display (LCD) TV has experienced great growth and is now rapidly gaining in popularity but the video chip 11 and the audio chip 12 of a conventional LCD TV are independently designed and disposed on a system circuit board, as shown in FIG. 1.
For circuitry simplification and cost-effectiveness, a single IC chip integrating therein a video circuitry module and an audio circuitry module is developed. As shown in FIG. 2, the conventional IC chip includes an interpolator 21, a digital-to-analog converter (DAC) 25 and a phase-locked loop (PLL) circuit 26 as a part of the audio circuitry module. The PLL circuit 26 generates a high-quality and high-frequency (n*Fs) clock signal according to a sampling clock signal with a frequency Fs (e.g. 32 kHz or 48 kHz) that is associated with a digital audio data, and the digital audio data is to be processed by the interpolator 21 and the digital-to-analog converter (DAC) 25 according to the clock signal with the frequency n*Fs. In other words, the interpolator 21 interpolates the digital audio data with reference to the high frequency n*Fs. The DAC 25 then converts the digital audio data into analog audio data with reference to the high frequency n*Fs.
The PLL circuit 26 is an analog circuit generally occupying a large layout area.